Back to EveryPatent.com
| United States Patent |
5,733,532
|
|
Raspanti
, et al.
|
March 31, 1998
|
Sun protecting cosmetic compositions comprising derivatives of
dibenzoylmethane, of benzophenone and of triazine
Abstract
Cosmetic compositions containing sunscreens against sun radiation ranging
from 280 to 380 nm, and their use for the protection of the skin from UV
radiation. The sunscreens comprise, with respect to the weight of the
composition:
a) from 1 to 10% of one or more derivatives of formula (I)
##STR1##
wherein Q is hydrogen or C.sub.1 --C.sub.4 alkoxy and G is C.sub.1
--C.sub.8 alkyl;
b) from 0.5 to 10% of one or more derivatives of formula (II):
##STR2##
wherein R.sub.1 is hydrogen or C.sub.1 --C.sub.8 alkyl and R.sub.2 is
hydrogen or an SO.sub.3 M group in which M is hydrogen, an alkali metal,
or an alkyl ammonium group; and
c) from 1 to 10% of one or more derivatives of formula (III)
##STR3##
wherein R.sub.3 is C.sub.1 --C.sub.8 alkyl and R.sub.4 has independently
the same meanings as R.sub.3 or is hydrogen or is an alkali metal;
with the condition that the weight ratio between the compounds of formula
(II) and the compounds of formula (I) is at least 0.5.
| Inventors:
|
Raspanti; Giuseppe (Bergamo, IT);
Malpede; Alverio (Bergamo, IT)
|
| Assignee:
|
3V Inc. (Weehawken, NJ)
|
| Appl. No.:
|
753735 |
| Filed:
|
November 29, 1996 |
| Current U.S. Class: |
424/59; 424/60; 424/400; 424/401; 514/245; 514/685; 514/687; 544/197; 568/331; 568/333 |
| Intern'l Class: |
A61K 007/42; A61K 007/44; A61K 031/53; A61K 031/12 |
| Field of Search: |
424/59,60,400,401
514/245,685,687
544/197
568/331,333
|
References Cited
U.S. Patent Documents
| 5639446 | Jun., 1997 | Raspanti et al. | 424/59.
|
Primary Examiner: Dodson; Shelley A.
Attorney, Agent or Firm: Griffin, Butler, Whisenhunt & Szipl
Claims
We claim:
1. A cosmetic composition comprising, in admixture with a cosmetic
substrate, with respect to the total weight of the composition:
a) from 1 to 10% of one or more compounds of formula (I)
##STR10##
wherein Q is hydrogen, straight or branched C.sub.1 --C.sub.4 alkoxy and
G is straight or branched C.sub.1 --C.sub.8 alkyl,
b) from 0.5 to 10% of one or more compounds of formula (II)
##STR11##
wherein R.sub.1 is hydrogen or a straight or branched C.sub.1 --C.sub.8
alkyl, R.sub.2 is hydrogen or an SO.sub.3 M group, wherein M is hydrogen,
an alkali metal or a mono- or polyalkyl-substituted ammonium group;
c) from 1 to 10% of one or more compounds of formula (III)
##STR12##
wherein R.sub.3 is straight or branched C.sub.1 --C.sub.8 alkyl;
R.sub.4 has the same meanings of R.sub.3 or is hydrogen or an alkali metal;
with the condition that the weight ratio between the compounds of formula
(II) and those of formula (I) is at least 0.5.
2. A cosmetic composition according to claim 1, wherein in formula (I) Q is
methoxy and G is ter-butyl.
3. A cosmetic composition according to claim 1, wherein in formula (I) Q is
hydrogen and G is isopropyl.
4. A cosmetic composition according to claim 1, wherein in formula (II),
R.sub.1 is methyl, R.sub.2 is hydrogen.
5. A cosmetic composition according to claim 1, wherein in formula (II),
R.sub.1 is methyl, R.sub.2 is SO.sub.3 M, wherein M is hydrogen.
6. A cosmetic composition according to claim 1, wherein in formula (III)
R.sub.3 and R.sub.4, that can be the same or different, are straight or
branched C.sub.4 --C.sub.8 alkyl.
7. A cosmetic composition according to claim 1, containing also zinc oxide.
8. A cosmetic composition according to claim 1, containing also titanium
dioxide.
9. A cosmetic composition according to claim 1, containing also other
sunscreens selected from the group consisting of: 4-methoxycinnamic acid
derivatives, salicylic acid derivatives, p-aminobenzoic acid derivatives,
benzylydenecamphor derivatives, 2-phenylbenzimidazole derivatives.
10. A cosmetic composition according to claim 1, containing as adjuvants
one or more components selected from the group consisting of thickening
agents, emollients, hydrating agents, preservatives, perfume.
11. A method for the cosmetic treatment of human skin when exposed to
sunlight consisting in applying a suitable amount of a cosmetic
composition of claim 1.
12. A method for the protective treatment of the human skin when exposed to
sunlight consisting in applying a suitable amount of a cosmetic
composition of claim 1.
13. A method for the stabilization of a cosmetic composition against UV
radiation comprising the addition to the cosmetic substrate from 2 to 10%
by weight with respect to the composition of a combination consisting of:
a) at least one compound of formula (I)
##STR13##
wherein Q is hydrogen, straight or branched C.sub.1 --C.sub.4 alkoxy and
G is straight or branched C.sub.1 --C.sub.8 alkyl,
b) at least one compound of formula (II)
##STR14##
wherein R.sub.1 is hydrogen or a straight or branched C.sub.1 --C.sub.8
alkyl, R.sub.2 is hydrogen or an SO.sub.3 M group, wherein M is hydrogen,
an alkali metal or a mono- or polyalkyl-substituted ammonium group;
c) at least one compound of formula (III)
##STR15##
wherein R.sub.3 is straight or branched C.sub.1 --C.sub.8 alkyl;
R.sub.4 has the same meanings of R.sub.3 or is hydrogen or an alkali metal;
with the condition that the weight ratio between the compounds of formula
(II) and those of formula (I) is at least 0.5.
14. A method for the preparation of a dermatological composition for the
protection of human skin from ultraviolet radiation, said method
comprising adding to a cosmetic substrate an
ultraviolet-radiation-protective amount of a photostabilizing mixture
consisting of:
a) at least one compound of formula (I)
##STR16##
wherein Q is hydrogen or straight or branched C.sub.1 --C.sub.4 alkoxy
and G is straight or branched C.sub.1 --C.sub.8 alkyl,
b) at least one compound of formula (II)
##STR17##
wherein R.sub.1 is hydrogen or a straight or branched C.sub.1 --C.sub.8
alkyl and R.sub.2 is hydrogen or an SO.sub.3 M group wherein M is
hydrogen, an alkali metal, or a mono- or polyalkyl-substituted ammonium
group; and
c) at least one compound of formula (III)
##STR18##
wherein R.sub.3 is straight or branched C.sub.1 --C.sub.8 alkyl and
R.sub.4 has the same meanings as R.sub.3 or is hydrogen or an alkali
metal;
with the condition that the weight ratio between the compounds of formula
(II) and those of formula (I) is at least 0.5.
Description
The present invention relates to cosmetic compositions, in the foregoing
called sun-protecting formulations, useful for the protection of skin
and/or hair from ultraviolet radiations containing photostable mixtures of
sunscreens.
BACKGROUND OF THE INVENTION
It is well known that sun radiations ranging from 280 to 400 nm are noxious
to human skin; in particular those radiations with a wavelength between
280 and 320 nm, the so-called UV-B radiations, cause erythema and
cutaneous sunburns, whose severity depends on the duration of the
exposition and on the kind of skin. It has been ascertained that also
radiations ranging from 320 to 400 nm, so-called UV-A and responsible of
skin tanning, can cause alterations in the skin and damages which may not
be disregarded, especially in cases of sensible skins or in case of
continuous exposition to radiations.
It has been demonstrated that UV-A radiation other than causing damages to
elastin and collagen, whose consequence is skin ageing, can also be the
cause of a number of phototoxic and photoallergic reactions. Moreover the
UV-B noxious action can be enhanced by the presence of UV-A (Willis et
al.: Journal of Investigative Dermatology vol. 59, 416, 1972).
Some compounds derived from cinnamic acid, 4-aminobenzoic acid and
benzylidencamphor are well-known and also used for the preparation of
sun-protecting formulations for the protection from the UV-B radiations.
These compounds, other than a more or less sufficient efficacy, do not
have a satisfactory photostability.
2-Ethylhexyl-cyano-.beta.,.beta.'-diphenylacrylate and
2-hydroxy-4-methoxybenzophenone show good photostability, however their
absorption is very low, therefore they have negligible efficacy.
2,4,6-Trianilino(p-carbo-2-ethylhexyloxy)-1,3,5-triazine is a sunscreen
described in U.S. Pat. No. 4,617,390 and recently marketed by BASF under
the trade name Uvinul.RTM. T 150. This sunscreen shows a high absorption
at about 310 nm, thus it has good efficacy and moreover it has a
satisfactory photostability. However, due to its poor solubility in the
usual cosmetic ingredients, practically the product was never successful
and it is seldom used.
In the U.S. Pat. No. 5,346,691 triazine derivatives are described, having
UV-B absorption at about 310 nm, which is very high. These derivatives not
only have a very good photostability, but also show very good solubility
in the solvents used for cosmetic formulations.
To date, on the contrary, sufficiently effective products for the
protection from UV-A are not yet available, even if in the patent
literature different compounds have been proposed; but their outcome is
not satisfying in practical use.
At present, the UV-A sunscreens (absorber) used in practice are limited to
benzophenone derivatives and to some dibenzoylmethane derivatives.
Benzophenone derivatives have a very good photostability, and can act both
as UV-B filters with absorption at about 290 nm, and as UV-A filters with
absorption at about 325 nm.
Nonetheless, the absorptions at two different wavelengths are relatively
weak, especially in the UV-A zone at 325 nm, therefore these compounds are
not able to provide a sufficient protection.
Among the derivatives of dibenzoylmethane,
4-methoxy4'-ter-butyldibenzoylmethane and 4-isopropyl-dibenzoylmethane are
those commercially known. These compounds show a Good absorption at 360 nm
and a fair solubility in the solvents usually employed in cosmetics.
However, their use is difficult, because they are not sufficiently
photostable (Int. J. Cosm. Science 10, 53, 1988). Accordingly, the
formulations containing these compounds can not guarantee a sufficient
protection against UV-A, since the protective filter is quickly degraded
by the radiation itself.
In order to avoid this quick degradation and give these UV-A filters some
photostability, in the patents GB 2,198,944, WO 91/11989 and WO 94/04131
particular combinations among UV-B filters belonging to the
benzylidencamphor and diphenylcyanoacrylate classes and the
dibenzoylmethane derivatives are proposed.
The results, however, still cannot be considered sufficient, because, even
with large amounts of the above UV-B filters, it is not possible to give
the dibenzoylmethane derivatives a satisfactory photostability.
For the photoprotection of the skin a large number of sun-protecting
formulations have been proposed and in this concern, a very wide patent
literature exists.
Therefore, the actual problem to be solved is the stabilization of
sunscreens in cosmetic formulations, in particular of dibenzoylmethane
derivatives. Moreover, another actual problem is the cosmetic treatment of
skin when exposed to sunlight such as to allow an agreeable tanning
without incurring in sunburns.
SUMMARY OF THE INVENTION
It has now surprisingly been found that photostable sun-protecting
formulations with protective activity against UV radiations ranging from
290 to 380 nm, i.e. UV-B and UV-A are obtained by means of combinations
comprising, with respect to the total weight of the composition:
a) from 1 to 10% of one or more compounds of formula (I)
##STR4##
wherein Q is hydrogen, straight or branched C.sub.1 --C.sub.4 alkoxy
group and G is straight or branched C.sub.1 --C.sub.8 alkyl,
b) from 0.5 to 10% of one or more compounds of formula (II)
##STR5##
wherein R.sub.1 is hydrogen or a straight or branched C.sub.1 --C.sub.8
alkyl, R.sub.2 is hydrogen or a SO.sub.3 M group, wherein M is hydrogen,
an alkali metal or a mono- or polyalkyl-substituted ammonium group;
c) from 1 to 10% of one or more compounds of formula (III)
##STR6##
wherein R.sub.3 is straight or branched C.sub.1 --C.sub.8 alkyl;
R.sub.4 has the same meanings of R.sub.3 or is hydrogen or an alkali metal;
with the condition that the weight ratio between the compounds of formula
(II) and those of formula (I) is at least 0.5.
Therefore, a cosmetic composition comprising in admixture with a cosmetic
substrate the components a), b) and c) as described above is an object of
the present invention.
Another object of the present invention is a method for the cosmetic
treatment or the protection of human skin when exposed to sunlight, said
method consisting in applying a suitable amount of a cosmetic composition
as described above.
A further object of the present invention is a method for the stabilization
of a cosmetic composition against UV radiation comprising the addition to
the cosmetic substrate a photostabilizing mixture as described in the
foregoing.
DETAILED DESCRIPTION OF THE INVENTION
Preferred compounds of formula (I) are those wherein Q is methoxy and G is
ter-butyl, or Q is hydrogen and G is isopropyl.
Preferred compounds of formula (II) are 2-hydroxy-4-methoxybenzophenone and
2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, both marketed by 3V SIGMA
under the trade names of Uvasorb.RTM.MET and Uvasorb.RTM.S 5.
Preferred compounds of formula (III) are those wherein R.sub.2 and R.sub.3
can be the same or different and are straight or branched C.sub.4
--C.sub.8 alkyl.
By means of the combinations according to the present invention,
particularly photostable sun-protecting formulations with protective
action both in UV-A and UV-B are obtained. Notwithstanding the fact that
the present inventors do not want to be bound to theoretical
interpretations, it may be supposed that the compounds of formula (II)
stabilize the UV-A filters of formula (I), which are per se not
photostable.
On the other hand, absorption in UV-B range of the compounds of formula
(II) is low, then their photoprotective action is very weak. It has
surprisingly been found that this action is enormously enhanced by the
presence of the compounds of formula (III).
The weight ratio between one or more compounds of formula (II) and one or
more compounds of formula (I) must be at least 0.5.
Examples of straight or branched C.sub.1 --C.sub.8 alkyl are methyl, ethyl,
propyl, butyl, pentyl, hexyl, heptyl, octyl and their isomers, in
particular isopropyl, terbutyl, 2-ethylhexyl.
Examples of straight or branched C.sub.1 --C.sub.4 alkoxy are methoxy,
ethoxy, propoxy, butoxy, and their isomers.
Examples of alkali metal are sodium, lithium and potassium.
Examples of mono- or polyalkyl-substituted ammonium are: mono-, di- or
triethanolamine and dodecylamine.
The derivatives of the dibenzoylmethane of formula (I), are described in
the U.S. Pat. Nos. 4,387,089 and 4,489,057. The commercial compounds are
Parsol.RTM.1789, (4-methoxy-4'-ter-butyldibenzoylmethane) by Givaudan and
Eusolex.RTM.8020, (4-isopropyldibenzoylmethane) by Merck. The compounds of
formula (III) are described in the U.S. Pat. No. 5,346,691.
Very often these sun-protecting formulations are in the form of
oil-in-water emulsion and containing, in variable concentrations, one or
more organic lipophilic and/or hydrophilic sunscreens, capable of
absorbing more or less intensely UV radiations of sunlight.
The kind of sunscreens and their suitable amount are selected depending on
the desired sun protecting factor (SPF). SPF is an index of protection and
is expressed as the ratio between the time of irradiation necessary to
reach the erythematogenic threshold in the presence of the UV filter and
the time necessary to reach the erythematogenic threshold in the absence
of the UV filter. SPF can be determined according to the method described
by B. Diffey and J. Robson in J. Soc. Cosmet. Chem. 40, 127-133 (1989).
It is thus possible to prepare sun-protecting formulations with high SPF,
suitable to guarantee a continuous protection of the skin also during
prolonged expositions to sunlight, so avoiding frequent and repeated
applications necessary for an effective protection.
According to the present invention, the photostable cosmetic compositions
suitable to skin protection from UV radiations with wavelength between 290
and 380 nm comprise a cosmetic substrate containing, with respect to the
weight of the composition, from 1 to 10% of one or more compounds of
formula (I), from 0.5 to 10% of one or more compounds of formula (II) and
from 1 to 10% of one or more compounds of formula (III), with the
condition that the weight ratio between the compounds of formula (II) and
those of formula (I) is at least 0.5.
The sun-protecting formulations according to the present invention, once
applied on epidermis, exert a protecting action against the noxious
effects of UV radiation, thus avoiding the formation of erythema or
sunburns or an early skin ageing.
The compositions of the invention can also be useful for the treatment,
then the protection, of hair or of make-up in decorative cosmetic.
According to the present invention the cosmetic formulations can be
solutions, lotions, emulsions of the water-in-oil or oil-in-water type; or
can also be in the form of gels, lipsticks, aerosol.
The compositions according to the present invention are prepared by
formulating the ingredients usually employed, such as for example oils,
fats, emulsifiers, moisturizing agents, humectants, emollients,
preservatives, surfactants, thickening agents, perfumes, pigments, dyes
and other else such as alcohols, polyols, electrolytes, siliconic
derivatives.
The more commonly used solvents are triglycerides of caprinic or caprilic
acid, castor oil, esters of fatty acids with isopropanol, propylene
glycol, glycerin, propylene glycol monomethyl- or monoethyl- or
monobutylether.
The cosmetic formulations according to the present invention other than
UV-absorber of formula (I), (II) and (III) can also contain other
complementary sunscreens active in UV-B or in UV-A, commonly used in
cosmetic, such as for example: derivatives of 4-methoxycinnamic acid,
derivatives of salicylic acid, derivatives of p-aminobenzoic acid,
derivatives of benzylidenecamphor, derivatives of 2-phenylbenzimidazole.
The sun-protecting formulations according to the present invention can also
contain inorganic pigments commonly used in cosmetics; such as for example
titanium oxide, zinc oxide, silica or aluminium oxide.
The present invention comprises also the protection of the cosmetic
compositions themselves from UV radiation by means of the addition of from
2 to 10% by weight with respect to the composition of a photostabilizing
mixture consisting of the combination of compounds of formula (I), (II)
and (III), described hereinafter. In this case it is a matter of
compositions whose components can undergo unwanted light-induced
degradation or colouring, as for example shampoos and hair lacquers, hair
dressing lotions, hair-dyeing compositions, make-up formulations, as nail
lacquers, foundation, lipstick. Preferred cosmetic formulations are the
ones for the protection of skin from sun radiations. Therefore, it is
another object of the present invention a photostabilizing mixture
consisting of:
a) at least a compound of formula (I)
##STR7##
wherein Q is hydrogen, straight or branched C.sub.1 --C.sub.4 alkoxy
group and G is straight or branched C.sub.1 --C.sub.8 alkyl,
b) at least a compound of formula (II)
##STR8##
wherein R.sub.1 is hydrogen or a straight or branched C.sub.1 --C.sub.8
alkyl, R.sub.2 is hydrogen or an SO.sub.3 M group, wherein M is hydrogen,
an alkali metal or a mono- or polyalkyl-substituted ammonium group;
c) at least a compound of formula (III)
##STR9##
wherein R.sub.3 is straight or branched C.sub.1 --C.sub.8 alkyl;
R.sub.4 has the same meanings of R.sub.3 or is hydrogen or an alkali metal;
with the condition that the weight ratio between the compounds of formula
(II) and those of formula (I) is at least 0.5.
The following examples further illustrate the invention.
EXAMPLE A--PHOTOSTABILITY
A solution of the sunscreens or their combinations in a solvent mixture
consisting of 70% ethyl alcohol and 30% isopropyl myristate was prepared.
From each solution 2 samples of 20 microliters were withdrawn by means of a
microsiringe and put on 2.times.5 cm microscope slides.
The samples so prepared were left in the air at room temperature for 30
minutes, as to allow ethanol evaporation. Subsequently, one of the two
samples was exposed to UV irradiation for 2 and 4 hours in a Suntest
Heraeus CPS+apparatus, fitted with a Xenon lamp and a filter system in
order to cut off UV radiation lower than 290 nm and IR radiation.
After exposition, the slides were washed with 50 or 100 ml of ethanol, as
to quantitatively solubilize the deposed material.
In the so obtained ethanolic solutions, without further dilution,
absorbance was measured in quartz cuvettes with 1 cm optical path by means
of a spectrophotometer Perkin-Elmer Lambda 2.
Photostability F was calculated as the percent ratio between absorbance at
the wavelength of maximum absorption of the exposed sample and the one of
the not exposed sample.
For the combinations, photostability was calculated only for the filter of
formula (I).
The results are shown in the following Table.
TABLE
______________________________________
F F
Sunscreens
g/100 ml solvent
2 hours 4 hours
______________________________________
A 5 23 14
B 5 94 86
C 5 100 100
D 5 100 100
A + B 5 + 5 89 78
A + B + C 2 + 2 + 4 87 76
A + B + D 2 + 4 + 4 91 85
______________________________________
A = 4methoxy-4ter-butyldibenzoylmethane
B = 2hydroxy-4-methoxybenzophenon
C = Compound of formula (III), R.sub.2 = terbutyl; R.sub.3 = 2ethylhexyl
D = Compound of formula (III), R.sub.2 = teroctyl; R.sub.3 = 2ethylhexyl
EXAMPLE 1--LOTION
______________________________________
Filter A 2.5 g
Filter B 2.5 g
Filter C 2.0 g
Octyl octanoate 46.0 g
Triglycerides C.sub.8 -C.sub.1
34.5 g
Dioctylcyclohexane 12.4 g
Perfume 0.1 g
______________________________________
The solvent mixture was warmed to 60.degree. C., while stirring, the three
sunscreens were added, stirring was continued for 10-15 minutes, perfume
was added after cooling.
EXAMPLE 2--O/W SUN CREAM
______________________________________
C.sub.12 -C.sub.15 Alkylbenzoate
5.0 g
Diisopropyl adipate 5.0 g
Karite butter 2.0 g
.alpha.-Bisabalol 0.5 g
Filter A 3.0 g
Filter B 2.5 g
Filter C 4.0 g
Stabylen 30 (R) (Thickening agent 3V SIGMA)
0.3 g
Synthalen K (R) (Thickening agent 3V SIGMA)
0.3 g
Abiol (R) (Preservative 3V SIGMA)
0.3 g
Methylparaben 0.2 g
Propylparaben 0.1 g
Glycerin 5.0 g
Aminomethylpropanol 0.5 g
Water up to 100.0 g
Perfume
______________________________________
The fatty phase was heated to 70.degree. C., sunscreens were added and
stirring was done for 10-15 minutes. Stabylen 30 and Synthalen K were
dispersed in water and the fatty phase was added under strong stirring to
the 70.degree. C. previously warmed aqueous dispersion. The resulting
mixture was neutralized with aminomethylpropanol, was cooled to 35.degree.
C. and preservatives, glycerin and perfume were added.
EXAMPLE 3--O/W DAY-CREAM
______________________________________
Triglyceryl methylglucose distearate
4.0 g
Glyceryl stearate 1.0 g
C.sub.12 -C.sub.15 Alkylbenzoate
7.5 g
Avocado oil 5.0 g
Diisopropyl adipate 5.0 g
Filter A 1.5 g
Filter B 2.0 g
Filter D 1.5 g
Synthalen K (Thickening agent 3V SIGMA)
0.2 g
Abiol (R) (Preservative 3V SIGMA)
0.3 g
Methylparaben 0.2 g
Propylparaben 0.1 g
Aminomethylpropanol 0.15 g
Glycerin 3.0 g
Water up to 100.0 g
Perfume q.s.
______________________________________
Operations were performed as described in Example 2.
EXAMPLE 4--O/W SUN MILK
______________________________________
PEG-7 Hydrogenated castor oil
7.5 g
Alcohols of lanolin in mineral oil
2.5 g
Octyl octanoate 7.5 g
Dioctylcyclohexane 5.0 g
Cetylstearyl octanoate 5.0 g
Filter A 3.0 g
Filter B 4.0 g
Filter C 3.5 g
Abiol (R) (Preservative 3V SIGMA)
0.3 g
Glycerin 5.0 g
Water up to 100.0 g
Perfume q.s.
______________________________________
The fatty phase was warmed to 70.degree. C. and the sunscreens were added.
70.degree. C. pre-heated water was added to the fatty phase under strong
stirring. After cooling, preservative, glycerin and perfume were added.
EXAMPLE 5--LIPSTICK
______________________________________
The base mixture was first prepared:
Beeswax 13.0 g
Carnauba wax 7.5 g
Lanolin 5.0 g
Isopropyl myristate 8.0 g
Mineral oil 3.0 g
Castor oil 63.5 g
______________________________________
85 g of this mixture were warmed to melt. 8 g of filter A, 7 g of filter C
and 9 g of filter B as well as perfume and dyes were added to the molten
mass, then it was diluted to 1000 g with castor oil and it was cooled at
room temperature.
Top